The present invention relates to a medical syringe. More particularly this invention concerns a prefilled syringe body ready for installation of a needle and use, and to a method of assembling such a syringe.
A syringe assembly has as described in commonly owned U.S. Pat. No. 5,785,691 a syringe body adapted to be filled with an injectable liquid and having an annular neck defining an axis and forming an axially outwardly open outlet adapted to hold a needle insert that blocks the outlet. The insert is formed with an axially through going passage so that a needle can be inserted axially through the passage of the insert into the body. A retaining collar engaged around the neck holds the insert in the outlet and a plug engaged in the passage fits over the retaining collar. A retaining sleeve fixed around the collar at the neck holds the collar on the neck and has an annular and axially outwardly directed end edge. A cup-shaped safety cap bearing axially inward on the plug has an annular and axially inwardly directed end edge confronting the retaining-sleeve edge and spaced axially therefrom by a gap which is bridged by a plurality of angularly spaced frangible webs unitarily formed with the sleeve and with the cap and extending from the cap edge to the sleeve edge.
The individual parts forming the cap subassembly, that is the insert and the cap, are made on different machines and must be mounted seriatim on the syringe body. Since this final assembly must be done after the syringe body is sterilized and filled, the parts forming the cap subassembly must also be sterile. Since these parts are made by different machines and at different locations, this entails a multipart sterilizing operation in the final clean room where the syringes are capped and prepared for transit.
It is therefore an object of the present invention to provide an improved syringe assembly.
Another object is the provision of such an improved syringe assembly which overcomes the above-given disadvantages, that is which is easier to assemble with the syringe body under sterile conditions.
A further object is to provide an improved method of assemblying a syringe.
A syringe assembly has according to the invention a syringe body adapted to be filled with an injectable liquid and having an annular neck defining an axis and having an axially outwardly open outlet. The neck is adapted to carry a needle. An elastomeric plug engaged axially inward with the neck closes the outlet and a holding ring is fixed to the neck below the plug. A retaining sleeve around the neck is fixed to the holding ring and a cup-shaped safety cap is fixed to the plug and has an end edge confronting the retaining sleeve and spaced axially therefrom. Frangible formations extend from the cap edge to the sleeve.
With the system of this invention the individual parts of the cap subassembly can be manufacture and put together in advance. Thus at the final assembly stage the cap subassembly is put onto the normally prefilled syringe body in a single operation made possible by the use of the holding ring. While the cap is made of a relatively hard and brittle material and similarly the syringe body is made of glass or a hard plastic, the holding ring is somewhat softer so that, even though the plug and holding ring are in the hard cap, they can be fitted over the hard syringe body while assembled together. The saving on steps in assembly is substantial, since the entire cap subassembly can be sterilized at the same time.
The safety cap according to the invention is formed with a pair of radially inwardly projecting ribs engaging the plug. They hold the plug solidly in place while still leaving space for sterilizing liquid or gas to flow through the cap subassembly.
The safety cap itself is formed with an internal annular shoulder and the plug has an enlarged portion engaged over the shoulder to fix the plug permanently in the cap once it is pushed into place. In addition the safety cap is formed with at least one radially throughgoing aperture that gives the end user the ability to see if the plug is properly in place before cracking off the cap. The ribs are normally provided 90xc2x0 offset from the windows so they cause the plug to bulge out the windows, further increasing the hold of the plug in the cap.
The retaining sleeve is formed with a radially inwardly open groove in which the holding ring is fitted. In another system the retaining sleeve is formed with an axially outwardly directed shoulder and the holding ring engages over the shoulder. In both situations the holding ring must be damaged or destroyed to separate it from the retaining sleeve once installed therein.
The holding ring itself according to the invention has an outwardly projecting and axially centered collar formed with an internal luer thread. Thus once the cap is broken off the retaining sleeve and removed along with the plug, a needle subassembly including an externally threaded luer-type base can be screwed right into the collar of the holding ring.
The retaining sleeve in accordance with the invention has a sleeve edge axially confronting and juxtaposed at a gap with the cap end edge. The formations include a plurality of frangible webs unitary with and extending axially between the edges. In addition a plurality of angularly spaced spacer blocks formed on one of the edges alternate with the webs and project at least partially across the gap toward the other edge. The webs are angularly equispaced about the axis and taper toward the retaining sleeve. Thus the axially inwardly effective force applied to the cap to force the holding ring over the neck will be transmitted by the blocks to the retaining sleeve while the frangible webs deform slightly elastically. The cap will not separate from the retaining sleeve unless it is tipped, twisted, or pulled axially out relative to it.
The neck is formed with an outwardly open seat receiving the holding ring. As a result the holding ring will be slightly elastically deformed as it is fitted over the neck, but the axial force to do this will be transmitted by the blocks from the cap to the sleeve carrying the holding ring. Any other force will cause the frangible webs to break well before the holding ring would pull of the neck, so the system is highly tamper proof. Any attempt to open and reclose the syringe would be evident.
The method according to the invention basically comprises the steps of supporting the holding ring on a support element, then fitting the plug over the support element adjacent the holding ring thereon and fitting the cap, formations, and sleeve over the holding ring and plug so that the plug seats and fixes itself in the cap and the holding ring seats and fixes itself in the sleeve. This action forms an integral assembly of the ring, plug, cap, formations, and sleeve which is then sterilized and fitted as one piece over the neck of the body until the ring locks in place thereon with the plug blocking the outlet. Of course according to the invention the ring, plug, cap, formations, and sleeve are fitted together under sterile conditions.
Once sterilized, the assembled ring, plug, cap, formations, and sleeve are encased in a hermetic envelope. This envelope is transported another clean room and there them to the syringe body. Production is therefore greatly rationalized and simplified with the sterile cap assemblies being produced in advance at another location and enclosed in respective hermetic envelopes. In another clean room at the fillers site the packages are opened and the sterile cap assemblies are fitted to the normally prefilled syringe bodies.